The invention relates to polymer foams and particularly to foams made from in situ polymerized polyesters in the presence of bitumen.
In another aspect, the invention relates to a process for the production of foamed polymeric materials comprising the in situ polymerization of polyesters in a solution of bitumen.
The formation of blends of certain polymers with a bitumen component has been proposed for the purpose of producing a water resistant coating material. For example, a blend of a liquid bitumen with a polyurethane prepolymer and a cross-linking agent is proposed in U.S. Pat. No. 3,179,610. Such compositions are said to be excellent for sealing surfaces, for filling cracks and as a binder for aggregates. In U.S. Pat. No. 3,385,802 a composition comprising an unsaturated polyester, coal and a polymerizable liquid vinyl monomer is cross-linked to form a protective coating. This material can also be foamed to provide an insulating layer.
Other blends of polymer and bituminous material which can be foamed are proposed in U.S. Pat. Nos. 3,177,164 (ethyl/vinyl acetate copolymer with asphalt), and 3,784,487 (novalak/bitumen). In U.S. Pat. No. 3,491,047 a bitumen is reacted with maleic anhydride which is then reacted with a polymer containing hydroxyalkylene, ester-substituted alkylene and alkylene monomer units. The products are said to have high strength and elasticity.
However, the prior art has not proposed any process for the production of a cross-linked polyester foam containing bitumen that is adapted to give a product that can be produced from the monomeric ingredients in a single operation, which is therefore adapted to production of articles by a "foam in place" single-step operation.
The present invention provides a polyester/bitumen product that can be formed in a single operation from the monomeric components and which has low heat conductivity and low water permeability. The polymeric product can be made more flexible or rigid by a simple variation of the relative proportions of the components. Moreover, the reaction by which the product is formed is so rapid that it is well adapted for use in the production of foam-in-mold articles. The reaction has the further advantage that the ingredients are mixed in the form of a liquid or a slurry so that extrusion or high pressure equipment is not required.
The polyester of use in the process of the present invention is fully described in commonly assigned, co-pending Application Ser. No. 646,215 which is hereby incorporated by reference.